The present invention relates to a rotational damper with a housing-fixed stator, a rotor and a transmission, which connects an coupling lever with the rotor of the transmission of the rotational damper.
The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention.
WO 2011/042085 A1 relates to an electric damper for damping relative movements between a first and a second mass, including a generator which is driven by the movement of the mass, and which is characterized in that the generator is integrated into a transmission, wherein a first transmission element which forms a stator is caused by the masses to rotate, which causes rotation of a second transmission element which forms a rotor and is coupled with the first transmission element in a directly or indirectly transmitted manner, wherein means for generating a magnetic field are provided either on the first or on the second transmission element. The transmission is a planetary transmission with a ring gear which forms the first transmission element, planetary gears which mesh with the ring gear, and with a sun gear which interacts with the planetary gears.
FIG. 1 of the present specification exemplary shows the course of the damping force of a conventional hydraulic damper, for example according to WO 2011/042085 A1, in traction and compression direction. The moment that can maximally be provided by a generator operated in the generator mode is the tilting moment. This also at the same time limits the maximally provided damping force. Curve x of FIG. 1 shows the course of the damping force of an electric damper. As soon as the tilting moment in the generator is exceeded, the damping force significantly decreases. The generator therefore has to be configured so that the damping forces, which occur during normal operation, are below the tilting moment of the generator. However, for exceptional situations (for example when the vehicle drives over a bump with high speed) the high damping force of a hydraulic damper has to be provided also with an electric damper. Increasing the tilting moment by configuring the generator accordingly inevitably leads to a very large and heavy generator.
Exceptional situations in which the maximal damping forces are required are encountered rather infrequently during operation of the vehicle. It is therefore not useful to dimension the generator in accordance with these maximal forces. Therefore electric dampers were developed in which the generator is merely configured in accordance with the damping forces occurring during normal driving operation. The high damping forces required for exceptional situations are generated by additional means which are activated via centrifugal force and are not activated at damper speeds below the trigger speed.
Thus DE 198 46 275 A1 relates to a system for roll stabilization of vehicles, in particular motor vehicles, in which actuators are provided, which have at least one sensor for detecting a roll parameter and at least one swivel drive which is arranged between halves of the front and/or rear chassis stabilizer, which actuators cause a pre-tensioning of the stabilizer halves for reducing or suppressing the roll movement and in case of rolling generate a counter moment on the vehicle superstructure depending on starting signals of the sensor. The swivel actuator is an electromechanical swivel actuator and means for blocking the pivoting of the stabilizer halves relative to each other are provided. The blocking means have a brake which opens electromagnetically or closes electromagnetically, and which in each swivel actuator is arranged between a respective swivel motor and a reduction gear of the swivel motor.
DE 10 2009 018 889 A1 relates to a roll stabilizer of a motor vehicle with an actuator which is arranged between two stabilizer sections and whose rotor is actuatable for a rotation of the stabilizer sections, wherein a braking device which acts on the rotor is characterized in that the braking device is configured as centrifugal brake which transfers a friction between the rotor and a stator. When the rotor is formed by a motor shaft of an electric motor, radially displaceable centrifugal bodies of the centrifugal brake are connected with the motor shaft. The centrifugal bodies and the stator are configured as friction partners for each other. The stator has a housing which receives the centrifugal bodies. The centrifugal bodies can be displaced radially outwardly against a spring element.
In electric dampers according to the state of the art the centrifugal brake, if provided, is integrated in the damper itself between the rotor and the stator of the generator. Consequently, the forces occurring in an exceptional situation are still introduced into the rotor/stator.
It would therefore be desirable and advantageous to provide an electric damper in which the generator in the exceptional situation is completely bridged.